LES LBM for turbomachinery
August 18, 2016 at 12:19 am #1851quadrupoleMember
Hello!rnrnI am interested in starting to use OpenLB with LES for computational aeroacoustics of turbo machinery applications. I am wondering how mature the code is such that it would be easy to mesh a rotor and stator configuration. Ideally one would be able to simulate the flow through a single rotor passage by using periodic boundary conditions. Is this possible? I have a few particular needs:rnrn1) The flow through the rotor is to be solved in a rotational domain, either by introducing the necessary coriolis forces or by having the mesh fully rotate. Is this possible? Judging by the recent youtube video it looks like it!rnrn2) Can the code cope with sliding boundaries? By this I mean imagine the rotor passage is linked to a single stator passage down stream in the axial direction. The rotor will rotate and slide past the stator inlet faces and eventually there will be no mutually touching faces. Can these sort of complicated connectivities be handled by OpenLB currently?rnrnThanks!rnrn rnrnAugust 18, 2016 at 11:25 am #2419robin.trunkKeymaster
Hi quadrupole,rnrnthe code should be capable of the setup you want to simulate.rnFor LES simulations Smagorinsky turbulence models are implemented, that are easy to use. Also OpenLB has a build-in meshing tool, so external libraries are not required. You can build your own mesh from geometric primitives or read in STL-files, or combine boith methods.rnThe simulation for the video you mentioned are done, by a frame change method. With functors you can apply coriolis and rotational forces to the fluid and apply velocity boundaries to the cylinder. This method requires far less computational cost than remeshing every timestep, by exploiting the advantage that the static part of the mesh is rotational invariant, is that also the case for your stator?rnTo apply periodic boundary conditions you can have a look a the “”forcedPoiseuille”” example in OpenLB where those boundaries are applied.rnAs far as I understand with the sliding boundaries you want to simulate that the rotor does not touch / collide the stator but there is no fluid node in between. This should also be possible, applying the mentioned frame change method together with appropriate boundary conditions.rnrnDoes this answer alle your questions?rnrnIf you want to get started with OpenLB, there will be a spring school in march:rnhttp://optilb.org/openlb/spring-school-2017rnrnBestrnRobinAugust 18, 2016 at 2:43 pm #2420quadrupoleMember
Hi Robin,rnrnMany thanks for your quick response. I have saved a video of an openFoam case which illustrates what I mean as I realise my explanation is not great 🙂 You can see it here: https://youtu.be/yXXGCwu8G9grnrnFor the time being I am interested in only simulating a single passage because I want to get a high resolution of the flow field but in the future maybe simulating the entire geometry is simpler. I am also wondering what the kind of parallel capabilities of the code are currently? I am looking at openLB as an alternative to classic CFD solutions for low mach number, low Reynolds number flow. The codes I am using have been scaling with large simulations utilising 16,000 cores and more, and I am wondering if openLB will allow the same? Otherwise due to the size of simulations involved its a no go for me.rnrnThanks!rnrnPS for some reason I don’t get reply alerts via email on the forums so apologies if I take some time to reply!rnrnAugust 19, 2016 at 4:39 pm #2426mathiasKeymaster
Hi,rnrnOpenLB is for sure a good choice using many cores. I am running simulations with more then 2000 cores and the parallel performance is great.rnrnBestrnMathias
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